The invention relates to a system and method for reactive power compensation in power networks.
Electric power networks are used for transmitting and distributing electricity for various purposes. Electric networks include multiple devices interconnected with each other to generate, transmit, and distribute electricity.
Electrical power networks experience voltage variations during operation that are caused by the variation in generation of the active and the reactive power by different power generating devices and variable consumption of the active and reactive power at different loads in the electrical power network.
Electric power networks to which large amounts of renewable power generation are connected can have large and rapid voltage variations at and around the points of interconnection that lead to excessive operation of voltage regulating devices such as on-load tap changing transformers and capacitors. Due to limited operating speeds of the voltage regulating devices, a constant voltage cannot always be maintained at all the network buses in the power network. Excessive operation of mechanically-switched transformer taps and capacitors leads to increased maintenance and diminished operating life of the switched devices.
One approach for mitigating the voltage variation mentioned above is to provide a closed loop controller, with or without voltage droop characteristics. The controller adjusts the reactive power supply to compensate the voltage variation using mechanically switched reactors and capacitors as well as dynamic devices such as static VAR compensators (SVCs) and static synchronous compensators (STATCOMs). More specifically, in some renewable power generation systems the closed loop controller adjusts the operating power factor of the power converter to adjust the reactive power for mitigating the voltage variation. The closed loop controller, however, may undesirably interact with other voltage controllers in the power network during this process. Furthermore, the closed loop controller tends to compensate for the reactive power demand of the network and connected loads, which leads to increased losses in the reactive power source and sub-optimal utilization of its dynamic capabilities.
An alternative approach for mitigating voltage variations in the power network is to individually compensate the self-induced voltage variation for each of the power generating devices. The amount of reactive power required for compensating a self-induced voltage variation is computed based on an approximate voltage drop equation which results in a constant power factor operation. However, this method tends to be inaccurate under high power conditions and may lead to overcompensation in the electric power network resulting in undesired voltage variations and increased losses.
Another approach is to compute the amount of reactive power based on the exact voltage drop equation which results in a variable power factor operation. However, this method is computationally complex and requires additional data.
Hence, there is a need for an improved system to address the aforementioned issues.